A range of wavelengths over which there is relatively little absorption of radiation by atmospheric gases. The major windows are the visible window, from ∼0. 3 to ∼0. 9 μm; the infrared window, from ∼8 to ∼13 μm; and the microwave window, at wavelengths longer than ∼1 mm. The infrared window loses much of its transparency under very humid conditions due to continuum absorption by water vapor, and can become completely opaque when clouds are present.